When Mom is out of Doonkleberries for her famous Doonkleberry pie, the boys set out to find some for her. Meanwhile, Perry and Dr. Doofenshmirtz find themselves across the ocean as Doofenshmirtz returns home to renew his Druesselsteinian driver's license. Back in Danville, Candace is convinced she has discovered the answer to her busting problem.

Paul the Delivery Guy discovers his job has a higher calling to save Danville as he makes stops at Phineas and Ferb's house, Doofenshmirtz Evil, Inc., Danville City Hall and the OWCA, in a special episode seen through his eyes. The rock band, Love Händel, returns for some musical accompaniment. Meanwhile, at Doofenshmirtz Evil Inc., Perry has lost the tools in his hat.